BMR Calculator

What is BMR (Basal Metabolic Rate)?

BMR is the number of calories your body burns at complete rest to maintain basic physiological functions like breathing, circulation, cell production, and organ function. It represents 60-75% of your total daily energy expenditure for most people.

The Mifflin-St Jeor equation used in this calculator is considered the gold standard, providing accuracy within 10% for most individuals when compared to laboratory measurements.

BMR vs TDEE: The Key Difference

BMR is your energy expenditure at rest. TDEE (Total Daily Energy Expenditure) includes your BMR plus calories burned through daily activities and exercise. For diet planning, you need your TDEE, not just BMR.

Factors That Affect BMR

Several biological and lifestyle factors significantly influence your basal metabolic rate:

• Age: BMR decreases by approximately 2-3% per decade after age 30 due to muscle mass loss
• Gender: Men typically have 10-15% higher BMR due to greater muscle mass and testosterone levels
• Body composition: Muscle tissue burns 6x more calories than fat tissue at rest
• Height and weight: Larger bodies require more energy for basic cellular functions
• Genetics: Can account for up to 30% variance in metabolic rate between individuals
• Thyroid function: Hyperthyroidism increases BMR, hypothyroidism decreases it
• Climate: Cold environments can increase BMR by 10-15% for thermoregulation

BMR Calculator Formulas Explained

Our calculator uses scientifically validated formulas for maximum accuracy:

1. Mifflin-St Jeor Equation (Default)

Men: BMR = (10 × weight in kg) + (6.25 × height in cm) - (5 × age) + 5

Women: BMR = (10 × weight in kg) + (6.25 × height in cm) - (5 × age) - 161

Developed in 1990, this formula is considered the most accurate for the general population with a 90% accuracy rate.

2. Katch-McArdle Formula (Advanced)

Formula: BMR = 370 + (21.6 × lean body mass in kg)

Used when body fat percentage is known. Most accurate for lean individuals and athletes.

3. Harris-Benedict Equation (Historical)

Men: BMR = 88.362 + (13.397 × weight) + (4.799 × height) - (5.677 × age)

Women: BMR = 447.593 + (9.247 × weight) + (3.098 × height) - (4.330 × age)

Created in 1919, this formula tends to overestimate BMR by 5-15% in modern populations.

How to Use Your BMR for Weight Management

For Weight Loss

Your BMR is the absolute minimum calories you need. Never eat below your BMR as this can slow metabolism and cause muscle loss. Instead, calculate your TDEE and create a 500-750 calorie deficit from that number.

For Muscle Gain

Eat 300-500 calories above your TDEE (not BMR) to support muscle protein synthesis while minimizing fat gain. Your BMR will increase as you build muscle mass.

For Maintenance

Eat at your TDEE level. Your BMR represents only 60-75% of your total daily calories needs when accounting for daily activities.

BMR vs RMR vs TDEE: Complete Guide

BMR (Basal Metabolic Rate)

Measured after 12 hours of fasting in a completely rested state. This is the theoretical minimum energy needed for survival.

RMR (Resting Metabolic Rate)

Similar to BMR but measured under less restrictive conditions. RMR is typically 10-20% higher than BMR and more practical for real-world applications.

TDEE (Total Daily Energy Expenditure)

Your BMR plus calories burned through daily activities, exercise, and digestion. This is the number you need for weight management planning.